In the production of liquid hydrocarbons from wells which are not free flowing it is common practice to use electric motor driven submersible pumps or similar type pumps with downhole motors. One problem associated with the use of downhole motor driven pumps, in particular, is that the liquid being pumped can have only a limited amount of gas entrained therein without developing operating problems which may damage the pump and generally cause unsatisfactory operation. Typically the entrained gas in the pump inlet fluid flow stream cannot exceed about fifteen percent by volume.
Accordingly, devices have been developed for use with submersible or similar types of downhole pumps wherein the fluid flowing toward the pump inlet is directed to undergo reverse flow and be directed along a spiral or helical flow path to effect centrifuging of the liquid and separation of gas therefrom. Certain types of electric motor driven submersible pumps also have a spiral type inducer section disposed just upstream of the pump impeller which is rotatably driven by the pump drive motor and effects some separation of gas from liquid flowing to the pump impeller. However, this type of separator consumes additional power since it exerts work on the fluid being pumped toward the primary liquid lifting pump. U.S. Pat. Nos. 4,481,020 to Lee et al. and 4,981,175 to Powers describe examples of motor driven rotating type gas-liquid separators for submersible well pumps.
Gas-liquid separators or so-called gas anchors have also been developed for downhole well pumps which force the gas-liquid mixture to undergo spiral or helical flow to effect separation of the gas and liquid due to centrifugal forces acting thereon. U.S. Pat. Nos. 3,128,719 to Jongbloed et al.; 3,048,122 to Hansen; 2,652,130 to Ferguson; 1,628,900 to Neilsen; 1,279,758 to Putnam; 2,398,339 to Watts and 2,843,053 to Carle disclose various arrangements of gas-liquid separators which effect a somewhat spiral or helical motion to the fluid mixture to effect separation of gas and liquid. Certain improvements in helical-type gas-liquid separators for downhole applications are also described in U.S. patent application Ser. No. 08/053,581 filed Apr. 27, 1993 by Weingarten et al. now abandoned.
However, there has been a continuing desire and need to develop improvements in gas-liquid separators for use in conjunction with downhole motor driven pumps, particularly electric motor driven submersible pumps, and wherein the gas content of the fluid mixture to be pumped is in the range of anywhere from fifteen percent to fifty percent by volume. It is to this end that the present invention has been developed.